Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are produced by performing a DC/DC, a DC/AC, and/or an AC/DC conversion by operating a switch loaded with an inductor or transformer. DC-DC converters, such as buck converters, are used in systems that use multiple power supplies. For example, in an automotive system, a microcontroller that nominally operates at a 5V power supply voltage may use a switched-mode power supply, such as a buck converter to produce a local 5V power supply from the 12V car battery. Such a power supply may be operated by driving an inductor using a high-side switching transistor coupled to a DC power supply. The output voltage of the power supply is controlled by varying the pulse-width of the time during which the switching transistor is in a conductive state.
In many applications, switched mode power converters supply a load with a constant voltage. In some systems, the power converter is configured to its operation when the input voltage, the load current or any other related parameter changes in a way that keeps the output voltage within a given limit. For example, load or line transients may require a fast reaction time. This task may be addressed by a voltage controller that measures the output voltage and adapts control quantities like peak current, switching frequency, duty cycle, or on time; so that the measured output voltage gets close to the desired output voltage.
Responding quickly to a voltage transient, however, may pose difficulties when the power supply is loaded with a large capacitive load. In such cases, a line transient may only affect a small change in the output voltage of the power converter. As such, linear controllers with high loop-gains or sensitive non-linear controllers may be employed to respond to such transients. High loop-gains may and sensitive controllers, however, may increase the risk of unstable operation and slow settling times.